Thrust reverser systems are used to decelerate a jet aircraft, and in particular to slow it down after landing, to slow it down during taxiing, and to aid it to back-up from a tight spot or a gate if needed. Reversing the exhaust jet flow from the engines provides the desired deceleration, especially on short runways, and slows down the aircraft to a safe taxiing speed thereby allowing the pilot to use the brakes on the taxiways.
Previous designs such as U.S. Pat. Nos. 2,968,150 and 3,610,534, sometimes referred to as four bar designs, the thrust reverser is built around the exhaust tailpipe. However, the protrusion of the actuation mechanism into the free air stream surrounding the reverser system, or engine nacelle, has the disadvantage of possibly incurring significant external drag which can penalize aircraft performance in various modes of operation and higher weight penalty.
U.S. Pat. No. 4,129,269, referred to in the industry as the single-pivot design, provides a light construction thrust reverser concept in which the movable doors and a reduced tailpipe form the exhaust system in forward thrust. The single-pivot design has the disadvantage of possibly permitting leakage of the internal engine gas flow between the stowed doors and the tailpipe. Exhaust flow leakage through the door/tailpipe system, do adversely impact engine thrust performance, fuel consumption and overall aircraft performance.
The ULTRA THRUST REVERSER SYSTEM is built on a continuous tailpipe to minimize external drag, while avoiding the drawbacks of leakage from the exhaust tailpipe. Exhaust plumes from both of the aforementioned conventional reverser designs are known to sometimes affect the aircraft control surface during reverse thrust operation. Both aforementioned designs therefore can require additional external surfaces to be attached to the aircraft pylon or other methods to divert the plume away from such control surfaces. Those additional external surfaces, mandated by considerations of compatibility and systems integration of the reverser with the aircraft, add further cost, weight, potential drag and vibration.
The new SQUARE ULTRA THRUST REVERSER SYSTEM design of the present invention optimizes primarily reverse thrust performance by redesigning the shape of the inner door surface to make it flat compared to the existing circular configurations, to maximize the efficiency of reverse flow in the forward direction and to reduce the likelihood of exhaust plume impingement on the aircraft surfaces. In the forward thrust mode, the SQUARE ULTRA is similar to the ULTRA THRUST REVERSER SYSTEM, in the fact that it comprises the design features which optimize forward thrust performance during the various modes of forward flight, and especially during the cruise mode where the aircraft spends most of its flight time. The new design preserves the prior design features in the same manner by combining lighter construction with the primary goal of optimizing internal and external flow aerodynamic characteristics. The rectangular trapezoidal door design deals effectively with aircraft/thrust reverser integration and compatibility issues, primarily the plume impingement on the aircraft control surfaces, discussed above, by using the sides of the rectangular doors as a buffer to prevent exhaust gases from escaping laterally and impinging on the aircraft surfaces, thereby providing an integrated means to control the plume and divert it away from the aircraft control surfaces. The reverse thrust efficiency is increased by using flat surfaces in the door design to deflect the majority of exhaust gases forward. The new design combines all the characteristics of the ULTRA THRUST REVERSER SYSTEM in addition to better reverse flow performance.
The housing design, in general, for the reverser system, including the actuators and the associated operating mechanism, can adversely affect the external air flow around the tailpipe causing external drag (due to the protrusion of reverser mechanisms in the free air stream around the nacelle thereby causing excessive drag during flight as in the case of the conventional four bar design. The housing design disclosed herein is based on the ULTRA REVERSER design, wherein it benefits from the fact that its housing not only affords no leakage path in the internal gas flow, but also that its housing does not protrude into the free air stream around the nacelle. Conventional single pivot reverser designs have the potential for significant flow leakage between such doors and the rest of the tailpipe. This defect is compounded by a further inability of that design to control the tailpipe exit area which adversely affects forward thrust. These two defects of this particular conventional housing design severely affect the engine's fuel consumption and performance, penalizing the aircraft's overall performance and range. On the other hand, excessive drag during flight incurred by the other conventional four bar housing design also penalizes the aircraft's overall performance and range. This drag is eliminated by using the housing design approach used on the ULTRA REVERSERSYSTEM.
Conventional construction techniques for target type thrust reverser components, single pivot or four bar, rely heavily on riveting together individual details and subassemblies of hardware, such as frames, inner skin, outer skin and other detail parts, A multitude of pieces of hardware and the extensive use of riveting increases the system weight as well as development, tooling and manufacturing costs. These aspects of design are adversely reflected in the aircraft's gross weight, payload, performance and cost of operation. The present invention is based on the lighter construction approach disclosed on the ULTRA REVERSER SYSTEM, including an integral exhaust tailpipe and integral rectangular/trapezoidal clamshell door construction, actuators and control systems. Integral construction of the tailpipe and doors provide a lighter, stronger structural system compared to conventional construction methods which are heavier, and labor intensive. The new system requires less investment in tooling. The incorporation of the side fairings into the rectangular/trapezoidal doors of the new design improves aerodynamic performance by providing blockage for plumes to prevent escaping and impingement on the aircraft fuselage and/or control surfaces, reduces gaps, and contributes to the reduction of external drag characteristics for better fuel consumption and enhances the overall aircraft/engine performance. The new SQUARE ULTRA design, like the ULTRA THRUST REVERSER SYSTEM uses two actuators to deploy the doors or in other configuration where four actuators are used to deploy the doors.